Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$69.81	3.146%	$72.0062	$72.01	$72.00	$72.00
Purchase #2	$249.67	10.817%	$276.6768	$276.68	$276.70	$276.70
Purchase #3	$24.58	11.223%	$27.3386	$27.34	$27.35	$27.30
Purchase #4	$88.55	3.716%	$91.8405	$91.84	$91.85	$91.80
Purchase #5	$141.87	6.325%	$150.8433	$150.84	$150.85	$150.80
Purchase #6	$247.63	3.192%	$255.5343	$255.53	$255.55	$255.50
Purchase #7	$66.44	9.615%	$72.8282	$72.83	$72.85	$72.80
7 purchase totals =	$888.55		$947.0679	$947.07	$947.15	$946.90